This proposal describes the continuation of the National Resource for Aplysia, the overall goal of which to provide consistently high-quality cultured sea hares, A. californica to researchers. A. californica is an important invertebrate (Opisthobranch mollusk) model system for health-related research, primarily in the neurophysiology and molecular biology of behavior and learning. We will continue to produce animals for research and to conduct basic research aimed at exploring new model uses and at improving the resource. The two aims of this project are: 1. Resource Production - Sales of animals to researchers in the US and internationally are projected to continue at present levels of 15,000 to 20,000 animals per year. This resource makes available A. californica at all life stages from eggs through mature adults by rearing animals in carefully controlled laboratory conditions. All life-stages are available in sufficient quantities to meet user demand throughout the year, eliminating reliance on wild-collected animals that have limited seasonal availability and are of unknown age and health status. The Resource also offers customized services for raising same-aged cohorts, using specific diets and harvesting tissues. New products to be offered in the coming grant period will include behaviorally validated mature and senescent animals. 2. Research Programs to support the Resource - We will extend two research projects initiated during the current grant period to create new Aplysia resources that we believe will expand the usefulness of this model system to researchers (1) Refinement of stages of aging to expand our understanding of stages of aging in the Aplysia model system and allow us to offer a more complete series of age-staged animals to our users wishing to study age-related phenomena and (2) Assessment of environmental effects on phenotype to investigate several approaches for culturing animals that somewhat mimic conditions in the wild.